The present invention relates generally to modular interface assemblies for weapons. More specifically, the present invention relates to a modular interface assembly that includes a rail system, which is clamped around and supported by the barrel nut of a firearm and further includes an optional sleeve element that can be installed to extend from the upper receiver rail over the top of the clamped rail system.
As the field of combat and commercial weaponry expands, numerous add-on enhancements have become available for attachment to standard firearms, thereby significantly upgrading the capability of the firearm. Of particular interest in the area of combat weapons is the well-known M16/M4 weapon system generally indicated at 10 in FIG. 1 (M16 and M4 are trademarks of Colt Defense, Inc.). The M16 has been in service for a number of years and will continue to be a popular rifle both in U.S. and foreign militaries for the foreseeable future. Generally, the M16/M4 weapon 10 includes a lower receiver 12, upper receiver 14, butt stock 16, and barrel 18. Referring to FIGS. 1 and 2, the barrel 18 is attached to the front of the upper receiver 14 by inserting the rear end of the barrel into a barrel-receiving receptacle 20 at the front end of the upper receiver 14. A pin 22 on the barrel 18 aligns with a notch 24 in the barrel-receiving receptacle 20 to insure that the barrel 18 is properly aligned with the upper receiver 14 when the barrel is installed into the barrel-receiving receptacle 20. The barrel 18 is held in assembled relation with the upper receiver 14 by a barrel nut 26 that is threaded onto the outside surface of the barrel-receiving receptacle 20. In this manner, the barrel nut 26 is rigidly engaged with the barrel receiving receptacle 20 and the upper receiver 14 of the weapon 10, while also serving to retain the barrel 18 in its installed position. A “delta ring” 28 (FIG. 1) encircles the barrel nut 26 and provides a spring loaded ring for attachment and support of the M16/M4 standard hand guards (not shown) between the delta ring 28 and a forward receptor cap 32 mounted at the front end of the barrel 18. A gas tube 29 extends from the upper receiver 14 to the receptor cap 32 at the front end of the barrel 18. The standard hand guards, when installed, encircle and protect both the barrel 18 and gas tube 29.
The newer models of the M16/M4 weapons 10 further include a mil-std 1913 dovetail rail 30 extending along the top of the upper receiver 14. This integrated receiver rail 30 provides a convenient mounting point for many types of enhancement devices such as scopes and other sighting devices. However, space on the upper receiver rail is limited, and many military personnel often have multiple sighting devices that are each tailored to perform in different combat situations. In addition, there are a variety of lighting devices, handgrips, etc. that could also be attached to the weapon 10 for enhanced use of the weapon 10. The difficulty is that there is simply not enough space on the integrated rail 30 provided on the upper receiver 14 to accommodate all of the desired accessories. Accordingly, the increasing development and refinement of laser sights, infrared lighting, visible lighting, night vision, and specialized scopes and magnifiers, and other accessories continues to drive the need for versatile and reliable integration systems that include additional mil-std 1913 dovetail rails positioned above or around the barrel 18 of the weapon 10 that can support this important equipment and yet stand the test of rugged military use and abuse.
As can be appreciated, the problem in attempting to meet this requirement by integrating a variety of modular attachments onto firearms is the inherent conflict between the unimpeded function of the gun barrel 18 and the desirability to be able to use the barrel 18 and/or other parts of the weapon 10 as a mounting platform for the desired modular attachments. The conflict arises from the fact that any additional weight and/or shocks that may be applied to the barrel from external attachments and accessories can adversely affect the alignment and reliable function of the weapon. It is also a requirement of most military contract specifications that the existing weapon not be modified for the purpose of mounting accessories to the weapon, thus insuring that such integration systems can be used universally on all existing weapons.
Accordingly, it has been realized that to obtain the best and most reliable performance of a rifle, the gun barrel 18 should be physically isolated relative to any other accessories or mounting systems, i.e., “free floating”. It is most preferred that nothing be attached to the gun barrel 18, thereby isolating the gun barrel 18 physically from outside elements and eliminating any bending and “droop” along the longitudinal axis of the barrel 18 that may be caused by excess weight near the front end of the barrel. The ideal mounting arrangement for modular attachments is one where the attachment is completely isolated from the gun barrel. This isolation serves two functional purposes. First, in operation, the temperature of a gun barrel can quickly rise to 900° F. This type of heat, as well as the physical shock transferred through the gun barrel during firing, can damage or destroy any attachments that are mounted in direct contact with the barrel. Additionally, the heat generated by the gun barrel is transferred to any devices mounted thereon, such as hand guards, thereby resulting in the direct transfer of enough heat to burn a user's hands and to potentially interfere with the operation of other attachments. The second issue compounding this problem is that if accessories are to be supported by the gun barrel, the gun barrel may need to be enlarged to support the added weight and shock forces. For example, a grenade launcher attachment not only introduces additional weight to the barrel, it also introduces substantial recoil in operation that is transferred into the firearm through the barrel. This in turn means more cantilevered stress on the barrel where it is joined with the upper receiver. The combination of heat and force applied to the barrel tends to pull the barrel chamber out of alignment with the bolt lead, thereby causing bolt lug and extractor failure, ultimately jamming the firearm.
Attempts have been made in the prior art to minimize the amount of weight that is transferred into the barrel by accessory mounts, wherein the accessory mounts are attached to both the upper receiver and the barrel. For example, U.S. Pat. No. 5,826,262 discloses a tubular rail received around the gun barrel. The rear end of the rail system is supported on the delta ring, which is secured around the barrel nut, i.e. supported on the receiver body. However, the front end of the rail system is supported on the receptor cap 32 mounted to the front end of the barrel 18 adjacent the front sight 34. Accordingly, the weight of any accessories mounted on the rail system is still partially carried by the front end of the barrel. In the case of a grenade launcher, the weight is considerable and could affect performance of the weapon.
There are also rail interface systems in the prior art that are supported directly from the upper receiver of the weapon and avoid attachment of any accessories to the gun barrel. For example, in U.S. Pat. No. 5,343,650 an extended rigid interface frame with upper and lower rails is shown joined to a firearm receiver and extends forward about the firearm's barrel to a head assembly replacing the firearm's normal front sight. A weaver type interface return portion is provided below the barrel from the head assembly to the receiver. A yoke braces the extended rigid frame receiver sleeve to the forward portion of the firearm's receiver. The distal end of the extended rigid frame receiver sleeve terminates in a front sight housing that connects the upper and lower rails and provides a housing for advanced laser and sensor components, and the standard front sight bead. The front sight housing is self-supported by the connection of the upper and lower rails running back to the yoke and secured to the top of the receiver. The barrel of the rifle is free floating in that it does not touch the extended rigid frame receiver sleeve in any manner. This permits greater shooting accuracy and protects sensitive electrical components within the front sight housing by isolating the front sight housing from the heat generated from the barrel.
In another example, the ARMS SIR system as disclosed in U.S. Pat. No. 6,499,245 also derives its support by extending a dovetail sleeve rearwardly over the dovetail rail 30 on the upper receiver 14 of the firearm and supporting the rail system in a cantilevered arrangement around the barrel (ARMS and SIR are registered trademarks of Atlantic Research Marketing Systems, Inc.). The ARMS SIR system has been well received by the military and has become popular with many military branches. However, it has been noted in field use that the dovetail sleeve introduces an added height to the existing mil-std 1913 rail of the receiver, and that this added height is not always desirable, particularly for some sighting devices that are popular with the military.
Accordingly, there is perceived to be a need for a unique modular interface rail design for mounting accessories to a firearm that supports the accessory without introducing loads or additional stresses into the barrel of the firearm while also providing an extended longitudinal rail for mounting accessories that is co-planar and in linear alignment with the existing interface rail 30 on the upper receiver 14 over the entire length of the top of the firearm, and in addition providing an optional sleeve over the upper receiver 14 for added height if desired.